The present invention relates to a new and improved construction of a bypass control apparatus or mechanism for turbocharged internal-combustion engines.
Generally speaking, the bypass control apparatus of the present development is of the type having an opening characteristic which is dependent upon the engine speed for a bypass valve located in a bypass line or pipe which connects a point of a boost or charging air pipe, located downstream of a compressor, with a point or location of an exhaust gas pipe located upstream of the turbine inlet.
As is well known in this technology, bypass mechanisms can be used to improve the partial load behaviour of turbocharged internal-combustion engines. In such cases, a fraction of the compressed boost air, which is a function of the momentary or instantaneous operating state of the engine, is withdrawn through a bypass line or pipe and delivered to a point or location of the exhaust gas pipe located upstream of the exhaust gas turbine. In this way, the engine receives more air than in the case of turbocharging without a bypass. For this purpose the bypass apparatus possesses a bypass valve which may be controlled by any engine load-dependent parameter or quantity and serving as a control magnitude. The valve-lift then is accomplished such that a large quantity of air is transferred during the no-load and lower partial load ranges and with increasing load a progressively decreasing quantity of air is transferred, until the valve completely closes near the full-load point of the engine and the transfer of bypass air is suppressed.
With a heretofore known bypass apparatus there is employed, for instance, as the control magnitude for controlling the bypass air stream, the pressure differential prevailing across the bypass between the compressed boost air and the exhaust at the turbine inlet.
It has already been proposed to utilize the engine speed as a control magnitude or quantity, but to the extent presently known, this concept has not yet been realized.